text: Every pipe or vessel is subject to heat loss when its temperature is greater than ambient temperature.  Thermal insulation reduces the rate of heat loss but does not eliminate it. Trace heating maintains the temperature above freezing by balancing heat lost with heat supplied. Normally, a thermostat is used to energise when it measures temperature falling below a set temperature value - usually between 3 °C and 5 °C and often referred to as the setpoint. The thermostat will de-energise the trace heating when it measures temperature rising past another set temperature value - usually 2 °C higher than the setpoint value.